March 14 is Pi Day, an annual celebration of the mathematical constant π (pi), which is the ratio of a circle's circumference to its diameter. The trillion digit ratio is rounded to 3.14.

For the rest of us, it's simply a day of deals on pizza, pastry and pot pies.

Pizza deals

Offers can vary by location so call ahead to be on the safe side. Also be prepared for restaurants to be busy.

Bertucci’s: All east coast locations are celebrating the “Week of Pi” by highlighting ongoing promotions like its “Two for Tuesday pizza special” called “Pi Twosday” this week and “Pi for Kids” Wednesday, which is the weekly kids eat free with $10.99 or more adult purchase special. Also this week, preview the new spring menu that rolls out March 19 and includes a Verde Pizza for “Pi Verde.”

Giordano’s: Get $3.14 off any online order Wednesday with code PIDAY314. Valid at all locations except Las Vegas Strip and Navy Pier.

Hungry Howie’s: With the purchase of any Howie Bread at regular menu price Tuesday and Wednesday, get a medium one-topping pizza for $3.14 with promo code PI18. Florida locations are not participating in this promotion.

Me-n-Ed’s Pizzeria: Get a personal one-topping pizza for $3.14 from 11 a.m. to 3:14 p.m. Wednesday for dine-in or take out. According to a Facebook post, you need to show a picture or email to redeem and one pizza per person.

Pagliacci Pizza: Buy any two slices for $3.14 or buy one 11-inch pizza and get one for $3.14 Wednesday.

Papa Murphy’s: Get a large, thin one-topping pizza for $3.14 for online orders Wednesday at participating locations. No promo code is needed.

Whether you love math or love to hate it, celebrate π Day with Pagliacci! We're adding something new to the equation - along with our usual buy two slices deal, we're doing a buy one get one 11" pie for $3.14. 3/14/18, mark your calendar! pic.twitter.com/gJ8jDNw4QL

Patxi's Pizza: Through Wednesday, buy one pizza, get one free when you dine-in.

Pi Pizzeria: The chain is celebrating Pi Day and its 10th birthday this week. Wednesday offers include: Buy one large pizza, get another pizza for $3.14 Wednesday, get a free “4 Hands Pi” pint glass with any full-price draft beer purchase and if your birthday is March 14, get a free large pizza with a birth certificate or government ID. And through Thursday, there will be an all-day happy hour at full-service locations.

Pie Five: All specialty pizzas are $3.14 at participating locations. Limit one per person.

Pieology: New and existing Pie Life members, buy a regular-priced custom or chef-inspired 11-inch thin crust pizza and get any thin crust pizza for $3.14 Wednesday with an email coupon. Limit one coupon per transaction, per visit and this offer isn’t valid on online orders or on orders placed over the phone.

The Pizza Press: Get a pizza for $3.14 with the purchase of a drink Wednesday.

Your Pie: Get a pizza for $3.14 Wednesday. Limit one pizza per person and no phone or online orders. Also through Wednesday, use the Your Pie loyalty app or #yourpieday on Facebook, Instagram or Twitter for a chance to win free pizza for a year or a GoPro Karma drone and Hero 6 camera package.

Other rounded specials

Bakers Square: Get $2 off any whole pie Wednesday or Thursday and double-crust fruit pies also will be baked with the pi symbol. Plus, get a free slice of pie from 10:30 a.m. until close Wednesday with any dine-in purchase for Free Pie Wednesday.

Bojangles’: Get three Sweet Potato Pies for $3.14 Wednesday while supplies last at participating locations.

Edwards Desserts: Starting at 7 a.m. ET Wednesday, the national frozen pie brand is celebrating Pi Day with a pie giveaway on its Facebook and Instagram pages. Fans can enter by commenting on either post with their favorite pie flavor. Once the posts reach 314 comments, 100 fans will win a free Edwards’ pie. For a bonus chance to win, comment at exactly 3:14 in any time zone.

Flying Star Cafe: Buy a slice of pie Wednesday and get a free scoop of ice cream.

Tony Duke’s: Try the limited-time menu item, Pi Fries, for $3.14 Wednesday. Also sign up for the chain’s loyalty program for a chance to win the fries for free.

Village Inn: Get $2 off any whole pie Wednesday and Thursday. Plus, with any dine-in purchase Wednesday from 10 a.m. to 10 p.m., get a free slice of classic fruit pie, Mint Brownie Blast or Coconut Cream for Free Pie Wednesday.

Pi Day wedding?

The company, which calls itself "an anti-establishment establishment," is transforming four of its pizza shops into pop-up wedding chapels for couples in D.C., New York City, Philadelphia and Baltimore.

The couples were selected in advance to get a free wedding complete with the ceremony, pizza, champagne, photography and flowers.

"We offer completely free weddings every Pi Day (March 14) to celebrate love, inclusion and unity," the company said in a statement, noting there will be at least a dozen weddings Wednesday.

The shops will remain open to the public Wednesday for pickup orders and include the Chinatown D.C. location, Astor Place store in New York City, Walnut Street location in Philadelphia and Baltimore’s Fed Hill.